Sampling Methods

• random


  produced by using a random technique such that every member of the target population has an equal chance of being selected
• systematic


  sample obtained by selecting every nth person
• stratified


  sample obtained by identifying subgroups (strata) in the target population and ensuring the sample reflects the proportions of people in each strata
• opportunity


  recruit people who are most convenient or available
• volunteer


  participants select themselves to be part of the sample through responding to advertisements
• random strengths


  unbiased- all members of target population have an equal chance of selection
• random weaknesses


  time consuming- requires a list of all members of the population and then contact all those selected

  may not truly be representative of population (chance)
• systematic strengths


  unbiased- ppts. selected using an objective system
• systematic weaknesses


  not truly unbiased/random unless you select a number using a random method
• stratified strengths


  representative sample- there is a proportional and randomly selected representation of subgroups
• stratified weaknesses


  time-consuming to identify subgroups
• opportunity strengths


  easy, convenient and cost-effective
• opportunity weaknesses


  biased- unrepresentative sample as it is drawn from a very specific area
• volunteer strengths


  easy and less time-consuming
• volunteer weaknesses


  volunteer bias- unrepresentative as may attract a certain 'type' of person